This invention relates to printable sheets of material. More particularly, this invention relates to printable sheets of material having a weight of at least 160 g/m2 to be inserted into a printing machine for printing.
The need for the mechanical printing of sheets of paper, cardboard or other materials is well known from practice. This is also effected especially by using conventional printing machines, laser printers, photocopying machines and other known printing and writing machines.
From time to time it is desired to use sheets of material that are as strong as possible, for example cardboard having a weight of at least 160 g/m2, preferably cardboard having a weight of from 220 to 300 g/m2. This is the case, for example, when sheets of cardboard having punched fields are to be used to produce visiting cards, as known, for example, from German patent No. DE 42 40 825.
However, such sheets of material, especially sheets of cardboard weighing more than 160 g/m2, can often not be drawn in and printed by conventional printing machines, especially conventional ink-jet or laser printers, or not without defects.
The reason resides in the fact that the relative stiffness and smoothness of the sheets of material at their ends often stands in the way of a perfect entry of the sheets of material at the printer inlet. The transport rollers used in printers cannot grip and transport the sheets of material cleanly when the ends of those sheets are too stiff and/or too smooth and/or do not come to rest in the ideal position between the transport rollers.
Although it is often possible in such cases to assist entry into the printer by feeding the sheets of material in manually, jamming of a printing sheet that is difficult to clear may occur time and time again inside the printer. Accordingly, there is a need for a printable sheet of material that is capable of smooth entry into a printing machine.
An object of the present invention is therefore to provide a sheet of material which, even at a weight of more than 160 g/m2, can be drawn in and printed by conventional printing machines in a faultless manner. This is achieved by reducing stiffness at an end from which the sheet in inserted into a printing machine. The reduced stiffness provides smooth and easy entry into printing machines and allows firm grips by transport rollers in the printing machine.